Refining of metal



July 28, 1942.

R. M. GIBSON REFINING OF METAL Filed June 4, 1941 INVENTOR 7PM flaw Patented July as, 1942 UNITED STATES -PATENT OFFICE 2,291,221 REFINING or METAL Robert M. Gibson, Pittsburgh, Pa. Application June 4, 1941, Serial No. 396,568

3 Claims.

In the production of steel by the Bessemer process a. bath of molten iron (typically pigiron) is blown through with air. By the inblown air the silicon, the manganese, and the carbon present in the iron are burned out, with a generation of heat suflicient to maintain the metal in molten state. Afterward manganese and carbon in measured quantities and to the required degree are restored to the metal, and other and various desired components of the ultimate steel as well. The converter lining may be acid or basic, and if basic the blowing with air (with or without the further addition of basic material) is continued, and in such continuance the phosphorus also is burned out of the molten metal.

The siliceous slag of the earlier portion of the refining operation is a by-product of little commercial value; the phosphorus-containing slag of the later portion is of much greater value.

The invention is found in method, whereby the basic Bessemer procedure may be practised with accuracy and expedition, and the slag expeditiously dealt with, in the course of operation, according to its changing character.

In the accompanying drawing means are diagrammatically shown which in their operation constitute a performance of the invention. The drawing is a view partly in vertical section and partly in side elevation of a furnace and of a converter assembled within it.

The converter 8 is arranged within the furnace walls 6. It may be understood that the converter 8 is mounted upon trunnions as is usual, and that conventional means are provided 4' for raising and lowering it to place upon its trunnions and for swinging it when it rests in place upon its trunnions.

Through the chamber wall from above and into the converter 8 extends an injection pipe 5. This pipe at its lower end is formed of or encased in refractory material 1, so as to maintain its integrity when in service it is at this its lower end immersed in a bath of molten metal within the converter. The pipe is suitably mounted and is movable vertically, conveniently by extension and retraction in axial direction, to the end that as operation progresses it may be advanced more deeply into the bath of molten metal and withdrawn more or less completely therefrom. The means for so ad justing the pipe may consist in a rotary pinion Ill, suitably borne in stationary housing H, and

meshing with a toothed rack H on the side of tated either manually or powerfully, to efiect the desired vertical adjustment of the pipe.

At its upper end 2 the pipe is hermetically tight, but provision is there made that the pipe shall constitute a tube through which the con- .dition of the molten metal within the converter through the lead I, and the pressure of the in-- troduced air is made suflicient not only to counterbalance the hydrostatic pressure of the molten metal in the converter and to keep the pipe open to its lower extremity, but to cause air emerging from the lower end of the pipe to bubble through the molten metal. It is in virtue of air injection that the receptacle (which otherwise would properly be called a ladle) becomes a converter.

The pipe 5 may additionally be provided toward its upper end with means for introducing such solid reagent material as dolomite or lime. Such-means are diagrammatically indicated in a bin 3 and a screw-conveyor 4 leading from the delivery end of the bin through the wall of pipe 5. Appropriate known means are provided for maintaining this portion of the apparatus the pipe. Manifestly, the pinion It may be rohermetically tight during the progress of operation.

The value of the furnace 6 is not only, or primarily, to conserve heat, but to retain the fumes and gases and dust that are produced in converter operation, that they may be properly conveyed to a stack or, perhaps, that their constituents and the heat that they carry may be turned to economic advantage. Again, it may be desirable to screen the converter from sight.

In operation, the receptacle 8 carrying a proper .charge of molten metal still in unrefined state (pig-iron, for example) is brought to position upon its trunnions within furnace 6. It is conveniently tipped on its trunnions to position such as that shown, and a second receptacle 9 is placed beside it, to receive spill from the rim of. receptacle 8. The furnace then is closed, the pipe 5 is caused to extend from above and its lower end Ito be plunged beneath the surface of and to be immersed in the bath of molten metal within receptacle 8. ;Air is applied, exeluding molten metal from the pipe, so that the pipe is free from end to end; and through pipe 5 air is admitted and caused to penetrate the molten metal. The air so admitted attacks primarily the silicon and secondarily the manganese and the carbon of the bath, and progressively burns these elements out. As this operation progresses a siliceous slag forms, floating upon the bath of molten metal. 7

As this initial burning-out operation progresses the pipe 5 is caused to advance downwardly in the bath of molten metal. Such downward advance is serviceable, both to give progressive effeet in the burning-out of the silicon (beginning near the surface and advancing more and more deeply) but also, by displacement, to effect a spilling of the slag as it accumulates, from the rim of receptacle 8 to the receptacle 9 that stands ready to receive it. Such downward advance of the pipe with progressive burning out of impurities is valuable in that the emergent air comes into immediate contact, not with refined but with unrefined metal; the reaction that progresses downwardly with the descent of the pipe is maintained at maximum intensity; and the overlying refined metal is protected from immediate access to it of the injected stream of air.

Meanwhile, through the open and unobstructed pipe 5 the condition of the molten metal is subject to detection, optically or otherwise. And thus in the progress of the refining operation the instant may be determined when the burning-out of the silicon is substantially accomplished and the point reached when the sequent burning-out of the phosphorus is to be accomplished. By such procedure it is possible.(and herein is a refinement upon conventional Bessemer procedure) to arrest the blowing while the desired small quantities of manganese and of carbon are retained.

When the desired point has been reached, and

v by the means described made known to the operator, the downward progress of the pipe 5 is arrested and its upward retraction begun. By the retraction, the spilling of slag from the rim of the receptacle is arrested. As the retraction of the pipe continues, basic material may be added to the bath, either through the pipe 5 by operation of conveyor 4 or otherwise. But in any case, whether the basic material for the phosphorus reaction is derived from the converter lining alone or is introduced, the burningout of the phosphorus goes forward; and, as it goes forward, in consequence of the retraction of the pipe 5, there is no spilling of the slag. The phosphorus-containing slag of this later portion of the refining operation is retained, floating upon the bath of refined metal; and may in appropriate manner be eventually removed and turned to economic use.

While I have dwelt upon the serviceability of the bin 3 and the conveyor 4 as means for introducing basic material to the bath, it is manifest that by these means other desired additions, such as term-manganese and other alloying additions may be introduced, either with basic material or alone; and, at the proper point in the progress of the refining operation carbon also may by such means he introduced. The parts 3 and 4 may be multiplied, and a plurality of bins for the same or for different materials may feed to the pipe 5. I

I have described the invention in application to the refining of iron. The refining of other metals is effected by the oxidation of adulterating material and its removal in the form of slag; and the invention is manifestly of general applicability in the refining of metal. Copper, notably, is a metal that lends itself practically to treatment according to the invention.

I claim as my invention:

1. In the production of steel by the Bessemer process the method herein described of effecting segregation of the successively produced siliceous and phosphorus-containing slags, which consists in blowing a charge of molten metal within a container through an injection tube immersed at its lower end in the bath and, as such blowin continues, lowering the tube within the bath with overflow from the receptacle of the resulting slag, and thereafter raising the tube, whereby the subsequently formed slag is retained.

2. In the production of steel by the Bessemer process the method herein described of effecting segregation of the successively produced siliceous and phosphorus-containing slags which consists in maintaining within a bath of molten metal within a receptacle an inthrust pipe filled with air under pressure, and, with injection of air into the molten metal, first advancing and afterward retracting the tube, whereby in the earlier portion of the operation slag spills from the rim of the receptacle and in a later portion the slag is retained.

3. In the production of steel by the Bessemer process the method herein described of effectin segregation of the successively produced siliceous and phosphorus-containing slags which consists in blowing a charge of molten metal within a container through an injection tube immersed at its lower end in the bath and, as such blowing continues, effecting first the descent of the tube within the bath with overflow from the receptacle of the resulting slag and second arresting the tube in such descent with cessation of such overflow and retention within the container of subsequently produced slag.

ROBERT M. GIBSON. 

